Unauthorized software use, or software piracy, has cost software producers and distributors billions of dollars worldwide. Consequently, there have been a number of methods developed to prevent software piracy.
One of the early approaches was to use various schemes to prevent copying of software. The was not popular with legitimate users, who wished to make backup copies. Further, these anti-copy schemes were based on methods that were so simple that programs were developed and sold that disabled the anti-copy mechanisms, thereby allowing unlimited copying. The whole approach was eventually dropped.
Another approach that is currently in use, involves a hardware key, sometimes referred to as a dongle. The dongle must be plugged into a port on the computer that is to run the software application in question. Functions are hidden within the application to be controlled that interrogate a key or keys in the dongle to verify authorization. The inconvenience of distributing and managing the dongle hardware devices has limited the use of this method to a very small market. Further, the method is not very secure since it is easy for an expert to find and bypass the software functions that interrogate the dongle.
Another approach has developed within the environment of local business networks; that is electronic license management. Within a network of computers, one particular computer is designated and set up as the license server for the whole network. This license server acts somewhat like the dongle described above, in that it provides keys and authorization information to other computers on the network. Protected applications contain hidden functions that interrogate the license server to verify authorization. These systems are not very popular since when there are network problems or when the license server itself fails, all associated applications stop working throughout the network. Further, like the dongle system, it is easy for an expert to find and bypass the interrogation functions hidden in the application.
Further, none of the above systems provide any protection against reverse engineering or unauthorized analysis and modification. These current anti-piracy systems provide no impediment to common reverse engineering techniques that can be used to discover confidential designs or to allow unauthorized modifications to the software.
An apparent solution, with some real security, might come from using technology developed for encrypting text. Executable software can be treated as binary text and encrypted using this well-known technology. The problem is that such encrypted software cannot execute or run. The only way to run it is to decrypt it back to its original form. Of course, once that is done, it can be copied or pirated.